This invention is directed to a hydraulic load sense system, and more particularly to a hydraulic load sense system for nonlinear applications.
Load sense systems are used widely throughout the power hydraulic industries. One of the main reasons of its popularity is the simplicity of control. Using Load Sense and Pressure Control appropriately, a load sense system is typically passive in nature which can be seen easily analytically. The difference between analytically found solutions and practical implementations lies in the choice of appropriate parameters such as clearance, spool area profile etc. Some of these parameters prescribe overall stability of the pump and in most cases these are figured out by several trial and error methods.
A complete hydraulic load sense system such as that found in an excavator is a naturally complex model. Components such as the engine, hydraulic pump, valves, uncertain load dynamics as well as uncertain operator behavior can instigate instability in various ways in a complex load-sense system. Many have confronted this situation in different ways. Most have ignored some practical aspects such as effect of load-sense control spool area etc. For a typical load sense system if the engine speed is assumed to be constant, the operator input to the valve is the only external input or effect into the system that drives the stability of the whole system. The variation in the load could be considered as external disturbance. Even though it is possible to formulate a control algorithm with one input for the whole system, the analytical solution would be very difficult to obtain because of the complexity of the involved nonlinear dynamics. Linearized models are good enough for predicted load situations, however the controls derived based on a linearized model may not be effective as nonlinear control under uncertain load conditions. Therefore, there exists a need in the art for a manner in which to address these deficiencies.
Therefore, an objective of the present invention is to prove a hydraulic load sense control that is based upon a nonlinearized model.
Another objective of the present invention is to provide a hydraulic load control actuated by operator command and load-sense spool effective opening area.
These and other objectives will be apparent to one of ordinary skill in the art based upon the following written description, drawings, and claims.